Fix few duplicate 'const' warnings

error: duplicate 'const' [-Werror=edantic]
diff --git a/skeletons/PrintableString.c b/skeletons/PrintableString.c
index 7b6828d..9a14938 100644
--- a/skeletons/PrintableString.c
+++ b/skeletons/PrintableString.c
@@ -41,7 +41,7 @@
 		return _PrintableString_code2value[code];
 	return -1;
 }
-static const asn_per_constraints_t asn_DEF_PrintableString_constraints = {
+static asn_per_constraints_t asn_DEF_PrintableString_constraints = {
 	{ APC_CONSTRAINED, 4, 4, 0x20, 0x39 },	/* Value */
 	{ APC_SEMI_CONSTRAINED, -1, -1, 0, 0 },	/* Size */
 	asn_DEF_PrintableString_v2c,